The invention relates to a housing, in particular housing of a tachograph, in particular of a tachograph of a commercial vehicle, with a battery holder for fixing on the housing by means of a battery receptacle designed as part of a basic body, with at least one fastening means for fastening the battery holder on the housing, with, in the state of the battery holder in which it is fitted with the housing, the fastening means being accessible exclusively from the interior of the housing.
The main focus of the use of the housing according to the invention is in the region of tachographs or devices for recording the working periods and rest periods of drivers of commercial vehicles. In addition to this preferred use, other uses are also conceivable, in particular those in which a high degree of security against manipulation is required. Owing to the high economic and legal significance of the data to be recorded in the case of tachographs, the recordings have to be reliably protected against manipulations. The safeguards relate both to the recording of data and the transmission of data and also the transmission and storage of the recorded data in the card memory. Relevant standards impose strict requirements on the safety standard to be achieved by the measures. In order to secure the data and maintain the operation if there are problems with an external power supply of the tachograph, an additional power supply of the tachograph by means of an integrated battery is indispensable. After a relatively long operating period of the device, in particular in the case of intensive use of the power provided by the battery, the battery needs to be changed, since the unit no longer provides the required voltage. For this reason, the battery which is integrated in the device or the components adjacent to it have to have arrangements which permit the battery to be changed. A previous solution of this technical problem makes provision for the battery to be inserted into a battery holder which is fastened to the housing wall by means of a screw in such a manner that the battery receptacle of the battery holder protrudes into the housing through an opening in the wall of the housing. The screw fastening the battery holder to the housing is accessible from the outside, with the result that, during a changing of the battery, after release of the screw the battery holder can be removed from the opening of the housing wall and the interior of the housing is thus accessible. The accessibility of the interior of the housing during the absence of a power supply conceals the risk of unnoticed manipulations of the electronic components situated there. In this connection, the changing of the battery is always a welcome pretext for changes to the device that are undertaken with fraudulent intent. Even a seal or safety device fixed on the fastening means of the battery holder is not capable of changing anything in this regard, since the maintaining of the operation of the device justifies the breaking open of the seal.
Starting from the problems and disadvantages of the prior art, the invention has set itself the object of arranging a battery in a changeable manner on a housing and at the same time of eliminating the possibility of the components situated in the housing being manipulated within the context of the battery being changed.
European patent application EP 0 774 736 A2 has already disclosed an arrangement of the type mentioned at the beginning, in which the fastening of the battery holder is extremely complicated and cost-intensive on account of the security against manipulation which is endeavored to be achieved. German laid-open specification DE 195 45 537 A1 describes a tachograph which can likewise have a battery in order to buffer the contents of the memory.
EP 1 006 767 A2 discloses an electronic component with a housing which completely surrounds a control unit which, inter alia, comprises a base and a battery holder. The base contains a battery-holder fastening part on which cutouts are provided. Connecting pins are formed on the battery holder and, in the assembled state, engage in the cutouts of the battery-holder fastening part. In order to change the battery, the control unit with the battery holder embedded therein has to be removed from the housing.
Starting from the problems and disadvantages of the prior art, the invention has set itself the object of arranging a battery in a changeable manner on a housing and at the same time of eliminating the possibility of the components situated in the housing being manipulated within the context of the battery being changed.
To achieve the object, a housing of the type mentioned at the beginning is proposed which has the features of claim 1. The subclaims show advantageous developments of the invention.